A flash memory device is a non-volatile memory device, which may be referred to as a Flash Electrically Erasable Programmable Read Only Memory (EEPROM or E2PROM). Nonvolatile memories are able to store data, even with power turned off. Memory cell arrays of flash memory devices (e.g., a NAND-type flash memory device) may be divided into a plurality of blocks, and each of the blocks may be constructed with a plurality of pages. In addition, each of the pages may be constructed with a plurality of memory cells sharing one word line. In general, each block may include 16, 32, or 64 pages, and each page may include 512 Bytes or 2048 Bytes of memory cells.
A flash memory cell may be defective as a result of a fabrication defect, or a flash memory cell may become defective during operation. A block including one or more defective memory cells may be referred to as “Bad Block”. If a number of bad blocks in a flash memory device exceeds a regulatory standard (e.g, more than 5), the flash memory device may be regarded as being defective.
However, a flash memory device including a number of bad blocks less than the regulatory standard may be capable of operating with the bad block(s). Using a copy-back operation, for example, data stored at any first page is stored at another page different from the first page. In this case, the first page may exist in a bad block and store valid data. The second page may exist in a block without defects.
If a bad block occurs, valid data stored at the bad block may be temporarily stored in a buffer memory (e.g., a DRAM or SRAM) by a page unit, and then written in another block of the defective flash memory. Since this copy-back operation reads data by a page unit and writes the read data again, it may have an undesirably long duration.